Children missing events that happened in the long past have drawn social concerns. When a child and his guardian wander away from each other, in the prior art, for example the child may send a short message to or have a voice call with the guardian by dialing the guardian's phone to tell the guardian his current position information. However, it is very difficult for the child to clearly describe the current position information as not being familiar with the ambient surrounding; furthermore, assume the child is confronted with a wicked abductor due to insufficient security awareness, he can hardly find his guardian. The guardian can only resort to news media or government authority to seek for the child, but the seeking effectiveness is undesirable.
Hence, it is urgently desirable to provide a method to ensure that the guardian can know the child's position information at any time.